The present invention relates to an electronic control method and apparatus for an internal combustion engine, and more particularly to an improvement of an electronic control method and apparatus as described and claimed in a copending U.S. patent application Ser. No. 856,509 filed on Dec. 1, 1977 in the name of Hisasi Kawai et al.
In such a control apparatus for the engine, a digital computer is adapted to calculate first and second values corresponding to optimum settings of fuel injectors and spark plugs in accordance with binary electric signals respectively indicative of the air intake of the engine and rotation speed of the engine upon receiving therein a timing signal and a reference signal, the timing signal being produced with a predetermined phase lag in relation to the reference signal.
To perform the above-noted calculation, the computer is programmed to calculate the first and second values from a first function describing a desired relationship among setting of the fuel injectors, the amount of air flowing into the engine and the rotation speed of the engine and from a second function describing another desired relationship among setting of the spark plugs, the amount of air flowing into the engine and the rotation speed of the engine. The first calculated value is converted by a comparator into the setting of the fuel injectors in response to the timing signal and the second calculated value is converted by another comparator into the setting of the spark plugs in response to the reference signal.
In the control apparatus, if the calculation of the first value is conducted during the activation of the spark plugs, the computer is inevitably disturbed by various noises caused by the activation of the spark plugs. This results in erroneous calculation of the first value. In addition, if the amount of air may not properly be detected, for example, due to damage of an air flow meter, the calculations of the first and second values will be erroneously conducted.